Arming switch

ABSTRACT

An arming switch for making an electrical circuit through connections thereto upon a sudden reduction in ambient pneumatic pressure. A pair of parallel connected contact blades spring loaded toward a stationary contact are held separated therefrom by a skirted piston in a cylinder. The cylinder behind the piston normally fill to ambient pressure around the skirt. Whenever there is a sudden reduction in ambient pressure, the pressure differential across the piston moves the piston away from the blades and permits the blades to close against the stationary contact. Inherent leakage around the piston prevents gradual ambient pressure changes from producing arming action.

United States Patent 1111 3,601,057

[72] lnventor Ralph S. Kline 1,030,196 6/1912 Lucier ZOO/61.19 Janesvllle, Wis. 2,899,516 8/1959 Smith 200/81 z g l 1969 Primary ExaminerBenjamin A. Borchelt 1 e e Assistant Examiner-Thomas H. Webb Patented 1971 Attorney-Gradolph, Love, Rogers and Van Sciver [73} Assignee Gibbs Manufacturing and Research Corporation Janesville, Wk.

[54] ARMING SWITCH ABSTRACT: An arming switch for making an electrical cir- 5 Clams 4 Drawing Flgs' cuit through connections thereto upon a sudden reduction in R, ambient neumatic ressure A of parallel connected 200/81 contact blades spring loaded toward a stationary contact are e arated therefrom a skirted piston in a ylinder The F42C 11/00 F429 5/00 cylinder behind the piston normally fill to ambient pressure [50] Field of Search ZOO/61.19, around the Skirt whenever them is a sudden reduction i 6115; 102/702, 70, 75 bient pressure, the pressure differential across the piston moves the piston away from the blades and permits the blades References Cited to close against the stationary contact. Inherent leakage UNlT E STATES PATENTS around the piston prevents gradual ambient pressure changes 783,399 2/1905 Blank ZOO/61.19 from producing arming action.

Patented Aug. 24, 1971 3,601,057

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awagwz gxwd ARMING SWITCH BACKGROUND OF THE INVENTION 1. Field of the Invention Arming switches of the type which remain inactive for indefinite, usually long, periods and then are called upon usually to operate only once upon the presence of certain conditions.

2. Description of the Prior Art Arming switches or other arming devices for military bombs, shells and the like are old, but usually depend upon inertial forces, timing devices, movement through the air or something similar for their operation. The only known arming device which depends upon pressure change for its actuation forms the subject of US. Pat. No. 2,940,392 issued to Donald A. Loren. This device, however, is complicated and responds to atmospheric pressure change after being triggered by an explosive charge. The purpose of that device is quite different from that served by the present invention.

SUMMARY OF THE INVENTION This invention relates to arming switches which are of general application under the particular circumstances to be discussed. Whether they are used to arm small bomb-type devices or other objects is no part of the present invention, this invention being limited to an electric switch used for actuating an electric circuit connected thereto (the arming operation) whenever desired. More particularly, the arming switch is especially intended to be used in association with others of its type in large numbers, such that a single operation can arm all of the switches simultaneously. As an example, which is not intended to be limitative, hundreds of small bombs in an unarmed condition can be packed into a canister or pod to be carried by an airplane and dumped substantially simultaneously to scatter randomly over an area. Each of these small bombs or other devices, such as land mines for instance, can have a battery powered circuit which is normally open (unarmed) and which should be closed (armed) just before the drop. Such electric arming schemes are a common arrangement and need no discussion, excepting that normally some external connection needs to be made to each bomb or similar device. This is satisfactory when only a few such devices are to be armed, but is not feasible under conditions where say 500 to 1000 small objects to be armed are simply packed randomly into a canister and then armed all together just before dumping from the canister.

The present invention provides inexpensive small switches, of the order of one-fourth, by five-eighths inches for example, one of which can be incorporated into each of the objects to be armed. The objects in the unarmed condition are then packed into a canister and the canister closed. Just before the drop, the canister is pressurized with air or other gas through a single connection to say 30 p.s.i.g. and the pressure then released. The principal object of the present invention is to provide novel switches which will function under these or similar conditions to arm all of the objects subject to this pressure release. That is, the switches should not arm when the canister pressure is increased, but only during the following pressure decrease.

Variations in procedure making use of these same switches might include pressurizing the canister before airplane takeoff so that only pressure release before the drop is required, or using a pressurized gas bottle attached to the canister as the source of gas for pressurization. These typical applications are, as previously pointed out, simply for purposes of orientation and are not of applicant's invention, this invention relating to the pneumatic pressure actuated arming switch itself.

From the above it will be appreciated that the object of this invention is to provide a small, inexpensive, arming switch which closes an electrical circuit upon a sudden decrease in ambient pressure and which does not function similarly upon a rise in ambient pressure orupon a gradual change in pressure in either direction.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a somewhat diagrammatic longitudinal medial sectional view through the arming switch of the present invention showing the switch in unarmed condition. Some of the elements in this view have been rotated so as better to present the invention;

FIG. 2 is a longitudinal medial sectional view similar to FIG. 1, but showing the switch in armed condition;

FIG. 3 is a transverse sectional view which may be considered as taken in the direction of the arrows along the line 3-3 of FIG. 1; and

FIG. 4 is a fractional transverse sectional view which may be considered as taken along the line 4-4 of FIG. 1 in the direction of the arrows, but with the elements shown in their proper orientation.

DESCRIPTION OF THE PREFERRED EMBODIMENT The arming switch is assembled from several relatively simple and inexpensive elements including a cylindrical casing 10 which is about one-fourth inch in diameter and five-eighths of an inch long in the specific example chosen for purpose of illustration. These dimensions are not critical, however, providing the other elements are in scale as will be understood.

The casing 10 is cut from a length of tubing which may be of metal or some plastic material having proper physical values. At each end it is recessed, as at 12 and 14 to take a closure disc 16 and a ring 18 respectively which are secured in the recesses by swaging the material of the cylinder 10 inwardly at its ends as at 20 and 22. The ring 18 at the left in FIGS. I and 2 is primarily a piston retainer and is formed of any suitable material and has an axial hole which permits free passage of air or other gas to and from the interior cylindrical space 24. The closure disc 16 is of an impervious material having electrical insulating properties and is sealed in place with cement 21 so as to form a substantially airtight end closure for the tube 10 at its right end.

A pair of spring metal contact blades 26 are welded at their ends to the external surface of a metal ring 27 at opposite sides thereof so as to extend essentially parallel to the ring axis. At an intermediate point the ring 27 is welded to a stem or pin 29 which is also parallel to the ring axis, but extends in the opposite direction relative to the blades 26. When the closure 16 is molded, the ring 27 is incorporated in the molding so that the blades 26 extend inwardly of the cylindrical housing 10 while the pin or stem 29 extends outwardly through the closure 16 to provide an external electrical terminal for the ring 27 and blades 26.

An axial stem 28 also extends through the end closure 16 to provide an outside terminal. This stem is similarly secured in the closure at the time of molding and extends inwardly of the cylinder 10 to a position about two-thirds of the distance toward the retainer ring 18, which is also the approximate free end position of the blades 26.

At their free ends the blades 26 are bent inwardly and then outwardly to form contact surfaces 31 which engage the stem 28 when the blades are free and inclined ramp surfaces 33 at their ends to facilitate wedging the blades apart. When the blades 26 are freed and spring inwardly into engagement with the stem 28 a circuit is completed between the stems 29 and 28 through parallel contact paths which insures against possible failure, because of dirt or the like, of one set of contacts. Of course, to save expense, only one of the blades 26 may be used if desired if the additional safety factor available with two blades connected in parallel is not important. If only one blade is used, it can be welded directly to the pin 29'and the ring 27 eliminated, or it can be made longer and extend through the closure 16 so as to provide the outside terminal.

For purpose of better disclosing the structure in one view,

A piston or plunger 40, made of soft rubber or a resilient plastic material of similar characteristics is positioned in the space between the free ends 33 of the blades 26 and the retainer 18. This piston is formed to provide a thin flexible skirt 42, the edge of which fits the surface of the cylinder 24. The free thin edge of the skirt is toward the closure 16 so that air under pressure will enter at the opening at ring 18 and depress the skirt slightly and pass through into the space between the piston and the closure 16. The piston skirt, however, acts as a check valve and prevents flow in the reverse direction excepting for slow leakage around the skirt. Such leakage although present is minor, and probably does not take place to any appreciable extent if the pressure differential across the piston is sufficient to expand the skirt against the cylinder sidewall. When the pressure differential is low, however, equalization in pressure across the piston can and does take place slowly.

To insure alignment of the skirted piston, it is shaped to provide longitudinally extending external ribs 44, six are shown, which have outer edges parallel to the axis and which fit loosely within the cylinder. These ridges prevent the piston from cocking, but do not appreciably inhibit the longitudinal movement.

The back side of the piston 40, the side toward the right, is generally reentrant, but is formed to have a cylindrical sleeve 46 at its axis which fits over the end of the stem 28 and can be slipped between the contacts 26 when theyare separated a sufficient amount. 80 long as the sleeve 46 is between the contacts 26 they cannot engage the stem 28. This is the condition shown in FIG. 1. When the piston is moved slightly to the left, however, the sleeve 46 will be withdrawn from between the blades 26, thereby permitting the blades to snap against the stem 28 under the influence of the springiness of the blades 26.

The device may be fabricated as follows. The closure element l6'with the spring blades 26, the ring 27 and stem 28 as a part thereof is picked up and inserted into the recess 12 in its cylinder member 10. The edge 20 is then swaged inwardly and the assembly sealed with cement 21. The piston 40 is inserted before or after the above operation and then the ring 18 is put in place and the edge 22 swaged. This accomplishes the assembly and the device then is in the condition illustrated in either FIGS. 1 or 2. By inserting a tool through the opening in the ring 18, the piston 40 can be pushed backwardly into the FIG. 1 position so that the switch is unarmed. If necessary, the tool can be used to deflect the piston skirt slightly if pushing the piston backwardly raises the pressure in the closed chamber too much. Clamping action of the blade ends 26' against the sleeve 46 and friction of the piston within the cylinder inhibits movement of the piston after assembly and so the device remains as in FIG. 1 until arming is desired. In this unarmed condition it may be incorporated into whatever device it is subsequently to arm and such devices may be put into a canister as previously mentioned. Because of slight leakage, subsequent gradual pressure changes due to temperature fluctuations if the canister is sealed or atmospheric pressure changes if it is not sealed will not shift the position of the piston. Also, since the mass of the piston is low in comparison with the frictional forces inhibiting its movements, the piston will not be shifted from the unarmed position by shocks or acceleration forces to which the device might be subject during handling or transit.

If desirable, the switch can be tested for proper operation and then reset as indicated above and then is ready for use.

Whenever it is desired to arm all of the devices in the canister having switches of this invention, the canister interior pressure is raised as previously described to a sufficient level, say to 30 p.s.i.g. Under these switch ambient conditions, air will flow through the ring 18, around the skirt 42 and into the chamber behind the skirt until the closed chamber pressure is essentially the same as the ambient, 30 p.s.i.g. in this example. Subsequently, when the canister pressure is released, there will be a pressure differential across the piston 40 of about 30 p.s.i.g. from right to left which forces the piston into the position of FIG. 2. This withdraws the sleeve 46 from between the contacts 26, thus permitting the contacts to snap against the stem 28 thus placing the switch in the armed condition.

If desired, the ring 18 may be eliminated and the end 22 simply swaged inwardly sufficiently to retain the piston 40. This makes it more difficult to prevent distortion of the cylinder internal diameter, however. Also the arrangement shown permits use of rings 18 having openings of different size for special purposes and also permits use of filter elements in place of the ring 18 for use in applications where contamination by dirt is likely.

I claim:

1. An arming switch for actuation upon an abrupt decrease in ambient pressure comprising electrical contact means spring loaded to one position when free, means providing a cylinder enclosing said contact means, said cylinder having a closed end and an open end, a piston movable in said cylinder and positioned toward the open end thereof relative to said contact means, said piston having pliable skirt engaging the interior surface of said cylinder, said skirt facing the closed end of said cylinder to permit gas to collapse said skirt slightly and flow around said piston from the open end of said cylinder to the closed end thereof to substantially equalize the pressures at the closed and open ends of said cylinder when the pressure at said open end tends to rise above the pressure at said closed end, said skirt substantially sealing against said cylinder surface to prevent flow from the closed end of said cylinder to the open end thereof when the pressure at said closed end is higher than at said open end, said piston when in one position toward said closed end engaging said contact means and holding said contact means in a position other than said contact one position, said piston when moved toward said open end freeing said contact means to move to said contact one position under the influence of said spring loading, said piston moving away from said piston one position toward the open end of said cylinder when the ambient pressure available at the open end of said cylinder abruptly drops a substantially predetermined amount below the previously prevailing ambient pressure.

2. The arming switch called for in claim 1 in which said contact means is a set of normally spring closed contacts and a member on said piston is adapted to lie between said contacts in the piston said one position and to be pulled from between said contacts when said piston moves away from said one position.

3. The arming switch called for in claim 2 in which the contract means is comprised of a pair of spring blades connected electrically in parallel and a substantially rigid contact member, the blades being spring loaded to engage said substantially rigid member, and the piston when in the said one position being adapted to hold the blades away from the substantially rigid contact member.

4. The arming switch called for in claim 2 in which the contact means is comprised of at least one spring blade and a second contact member, the blade being spring loaded to engage said second contact member when said contact members are free, and the piston when in the said one position being adapted to hold the blade away from the second contact member. 7

5. The arming switch called for in claim I in which means providing access to the piston is provided for moving the piston to the piston said one position to reset the switch to unarmed condition. 

1. An arming switch for actuation upon an abrupt decrease in ambient pressure comprising electrical contact means spring loaded to one position when free, means providing a cylinder enclosing said contact means, said cylinder having a closed end and an open end, a piston movable in said cylinder and positioned toward the open end thereof relative to said contact means, said piston having pliable skirt engaging the interior surface of said cylinder, said skirt facing the closed end of said cylinder to permit gas to collapse said skirt slightly and flow around said piston from the open end of said cylinder to the closed end thereof to substantially equalize the pressures at the closed and open ends of said cylinder when the pressure at said open end tends to rise above the pressure at said closed end, said skirt substantially sealing against said cylinder surface to prevent flow from the closed end of said cylinder to the open end thereof when the pressure at said closed end is higher than at said open end, said piston when in one position toward said closed end engaging said contact means and holding said contact means in a position other than said contact one position, said piston when moved toward said open end freeing said contact means to move to said contact one position under the influence of said spring loading, said piston moving away from said piston one position toward the open end of said cylinder when the ambient pressure available at the open end of said cylinder abruptly drops a substantially predetermined amount below the previously prevailing ambient pressure.
 2. The arming switch called for in claim 1 in which said contact means is a set of normally spring closed contacts and a member on said piston is adapted to lie between said contacts in the piston said one position and to be pulled from between said contacts when said piston moves away from said one position.
 3. The arming switch called for in claim 2 in which the contract means is comprised of a pair of spring blades connected electrically in parallel and a substantially rigid contact member, the blades being spring loaded to engage said substantially rigid member, and the piston when in the said one position being adapted to hold the blades away from the substantially rigid contact member.
 4. The arming switch called for in claim 2 in which the contact means is comprised of at least one spring blade and a second contact member, the blade being spring loaded to engage said second contact member when said contact members are free, and the piston when in the said one position being adapted to hold the blade away from the second contact member.
 5. The arming switch called for in claim 1 in which means providing access to the piston is provided for moving the piston to the piston said one position to reset the switch to unarmed condition. 